Refrigerating apparatus with magnetic latch



3, 1959 E. J. MILLER ET AL 2,871,676

REFRIGERATING APPARATUS WITH MAGNETIC LATCH Filed July 6, 1954 lol INVENTOR.

\ Edwin J. Miller and 'l By Ke/ I) K Kes mg The/7 Artur ray REFRIGERATING APPARATUS WITH MAGNETIC LATCH Edwin J. Miller and Keith K. Kesling, Dayton, Ohio, assignors to General Motors Corporation, Detroit, Micln, a corporation of Delaware Application July 6, 1954, Serial No. 441,262 13 Claims. (Cl. 62-264) This invention relates to refrigerating apparatus and more particularly to a door latch.

A number of problems present themselves in designing a latch for a refrigerator which are not present in designing latches for general application. One of the problems is that of providing a latch which exerts a suflicient pressure on the door to partially compress the door seal and one which at the same time is easy to operate merely with the press or pull of a finger or a push by ones arm. of providing a refrigerator ier problem is that latch which precludes trapping children in the refrigerator when not in use. A large number of children are trapped in abandoned or unused refrigerators each year because the door latches on the refrigerators cannot be operated from the inside of the refrigerator. It is recognized that a large number of internal latch release mechanisms have been devised from time to time but these are objectionable from the standpoint that small children become panicky when locked in a dark refrigerator and are unable to operate the latch release mechanism. Furthermore, many of these latch release mechanisms have been impractical from the cost standpoint or for other reasons.

It is one object of this invention to provide a refrigerator having a latch which is automatically rendered ineffective to trap children when the refrigerator has been abandoned or temporarily disconnected from a source of electricity.

Still another object of this invention is to provide a safety latch which may be manufactured at a low cost.

A further object of this invention is to provide a latch which has the necessary holding power to properly compress the sealing gasket and which at the same time is easy to operate.

It is another object of this invention to provide an electromagnetic latch which has a minimum number of moving parts and which does not require a continuous supply of electricity for sustaining its holding ability.

More particularly it is an object of this invention to provide an electromagnetic device in which a portion of the core is in the form of a permanent magnet which sustains the holding properties of the magnet after the current flow through the Winding of the electromagnet has been interrupted.

Still another object of this invention is to provide an improved form of electromagnetic latch in which the holding force may be broken by applying a mechanical force or by reversing the flow of current through the coil of the electromagnet.

Further objects and advantages of the present invention will be apparent from the following description, reference being bad to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

in the drawings:

Figure l is a perspective view somewhat schematic showing the invention applied to a modern refrigerator;

Figure 2 is an enlarged fragmentary vertical sectional nited States Patent 0 view showing the construction and arrangement of the latch;

Figure 3 is a horizontal sectional view of the apparatus shown in Figure 2 of the drawing; and,

Figure 4 is a schematic view of the electrical circuit.

Referring now to the drawing wherein a preferred embodiment of the invention has been shown, reference numeral it; generally designates a modern refrigerator having a frozen food storage compartment 12, an unfrozen food storage compartment 14 and a machinery compartment 16 located directly beneath the compartment 14. A conventional refrigerating system comprising a compressor 18, a condenser 20, refrigerant flow restrictor 22, freezer compartment evaporator 24 and food storage compartment evaporator 26 is used for refrigerating the storage compartments in accordance with present practice. A light 27 is provided for lighting the compartment 26 whenever the door 30 is opened. The refrigeration system is preferably of the type shown in Patent No. 2,672,023 to which reference is hereby made for a more complete description of the refrigerating the refrigerator light 27, through the usual 110 volt alternating current supply line 28. A thermostatically operated switch 29 serves to cycle the refrigerant compressor in accordance with refrigeration requirements as more fully explained in the aforesaid patent.

For purposes of illustration, there has been shown a refrigerator of the type wherein a single refrigerator door 30 is provided for closing both of the compartments 12 and 14 whereas separate doors could be provided for each compartment in which case separate latches would be provided for the doors. This door shown is provided with a latch mechanism generally designated by the reference numeral 32 which is adapted to hold the door in a closed position with a force sufiEicient to partially compress the sealing gasket 34. The latch includes a magnet portion generally designated by the reference numeral 36 and a keeper or armature 38.

The latch is an electromagnetic latch in which a temporary direct current electric charge is used for energiz ing the same in a manner to be explained more fully hereinafter and in which a permanent magnet maintains the electromagnet magnetized after the current is turned off. This latch produces a very strong pulling effect which is permanent as long as the refrigerator door is closed. After the door is opened so as to disrupt the metallic flux path by pulling the keeper away from the magnetic poles of the magnet this strong pull will not be restored until another temporary electric charge is produced. Without the electric charge the pull is only about as much as it is after being charged. Thus, the latch will provide a strong pull-in force for compressing the door sealing gasket 34 and for holding the door closed provided the energizing coil 54 of the magnet is momentarily energized as the door is closed to provide the initial magnetization of the magnetic circuit. It has been found that this strong pull continues after the current flow through the coil of the magnet has ceased and the pull is destroyed only when the door is reopened so as to break the flux path through the metallic parts of the flux circuit.

Reclosing of the door without supplying current to the magnetizing coil, such as when the refrigerator is disconnected from its power source, does not reestablish the maximum strong pull as only ,4 or thereabouts of the maximum pull will then be exerted even though the metallic flux path is reestablished by movement of the keeper 38 into contact with the core of the magnet 36.

The latch mechanism includes a magnet assembly gen erally designated by the reference numeral 36 which is adapted to be supported on the stationary part of the cabinet and a keeper or armature 38 which is adapted to be supported on the door 30. Insofar as certain aspects of this invention are concerned, the magnet could equally well be mounted on the door and the keeper could be mounted on the cabinet.

The magnet comprises a magnetically soft U-shaped iron or steel core 4% which has secured thereto a central post which comprises a magnetically soft iron or steel portion 42, a magnetically hard portion :4 which preferably comprises a magnetic alloy such as Alnico 5 and a magnetically soft iron or steel portion 46. The portions 40 through 46 are held in assembled relationship by means of a threaded post 48 which also serves to mount the magnet assembly on a sheet metal bracket so which is secured to the side wall of the refrigerator housing asshown in Figures 2 and 3 of the drawing. A rubber grommet 52 is provided between the post 48 and the bracket 5%) for yieldably supporting the magnet in place on the refrigerator cabinet. A magnetizing coil 54 surrounds the central post 42 as best shown in Figure 2 ofthe drawing.

The keeper 38 is pivotally supported adjacent its lower end on a fixed pivot element and is provided with an .outwardly projecting actuator arm 62 which carries a nylon roller 64 adjacent its outer end as best shown in Figure 2 of the drawing. The drawing shows the relationship of the keeper to the magnet when the refrigerator door 30 is in the pull-in position before the gasket 34 has been compressed. The keeper is biased into the position in which it is shown in Figure 2 by means of a compression spring assembly 66. Upon energization of the coil 54 the door will be pulled shut with the gasket 34 properly compressed.

The latch actuator which is used for breaking the magnetic pull and for opening the door comprises a member 68 which is pivotally supported on a stationary pin '70 carried by the door framework. The actuator 68 is provided with a cam projection 72 which is adapted to operate against the roller 64 so as to cause pivotal move ment of the keeper 3% about the pivot 69 when it is desired to break the magnetic flux path for reducing the holding force of the magnet.

As best shown in Figure 4 of the drawing, the coil 54 of the magnet is arranged in series with a first switch and a second switch 1432. A rectifier 104 is provided in the line which connects the magnet to the main volt power lines generally designated by the reference character 28. The switch 102 is a door operated single pole, double throw switch which closes the circuit to the refrigerator light 27 when the refrigerator door is opened and which closes the circuit to the coil 54 when the door is closed. The switch 100 is mounted on the keeper 38 as best shown in Figure 2 and is adapted to be operated by means of a magnetic actuator 108 which is pivotally supported at 110 on the arm 62. The actuator 108 is biased into the full line position or the switch closing position by means of a spring 1E2. When the refrigerator door is moved to the closed position, the switch 102 will automatically be closed by virtue of the fact that the door is closed and the switch lilil will be closed up until the keeper 38 moves into contact with the core of the magnet at which time the actuator 108 will be attracted to the projection 109 on the keeper '38. When the switches 100 and 102 are both closed the coil 54 of the magnet will beenergized with the result that a very strong magnetic flux field is set up in the keeper as well as in the core of the magnet the instant that the keeper contacts the core of the magnet. This strong magnetic field serves to move the switch actuator 108 from the full line position in which it is shown in Figure 2 to the dotted line position so as to open the switch 100. Opening of the switch 160 interrupts the flow of current to the magnetizing coil 54 but this does not destroy the strong pull of the magnet due to the fact that the permanent magnet portion 44 serves to maintain a strong magnetic flux throughout the entire core of the magnet so long as the keeper is in contact with the magnet. Once the metallic path for the magnetic flux is broken, such as by pivotal movement of the keeper 38 in response to the actuation of the element 63, an air gap is introduced which greatly reduces the effectiveness of the magnet. The construction and arrangement of the magnet is such that the permeance ratio is very high when the keeper engages the magnet but is reduced when the keeper is pulled away from the magnet. Reclosing of the door with the power disconnected restores the high permeance ratio but not the high magnetic induction which was greatly reduced when the permeancc ratio was reduced.

Since there may be times when the power supply may be momentarily interrupted or may be interrupted for several hours or more and since the latch depends on a power supply for restoring the high magnetic induction required for holding the door in the fully closed position with the gasket compressed, it is desirable that some small force be provided which will enable the door to be held in a pull-in position without full pressure being applied to the gasket. For this purpose there is provided a steel spring element which has its ends hooked over the ends of the keeper 38. .This spring element is bowed as shown in Figure 2 so as to move into direct contact with the central post of the magnet when the door is in the pull-in position but before the gasket has been compressed with any appreciable force. The pull of the permanent magnet 44 on the spring 126 is suflicient to hold the door in the pull-in position but is not enough to hold a small child locked into the food compartment of the refrigerator if the current to the refrigerator were turned off or the refrigerator were disconnected such as it would be if left standing on a rear porch or on a junk pile.

By virtue of the above described construction and arrangemennthis latch then constitutes a safety latch which has the pull-in power of a strong electromagnet when the refrigerator is in normal use and has enough power to hold the door closed when the current is ofi for any reason but is incapable of holding a child trapped in an abandoned or disconnected refrigerator.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. In a refrigerator; cabinet means forming an insulated food storage compartment having an access opening; a door for said access opening; gasket means between said door and said cabinet means; a light in said compartment; an evaporator arranged in thermal exchange relationship with the contents of said compartment; means including a motor-compressor unit for supplying liquefied refrigerant to said evaporator; electromagnetic latch means for holding said door in a closed position with said gasket in a compressed condition; a common alternating current power supply means for said light, said motor-compressor unit, and said magnetic latch means; switch means operated by said door for selectively supplying electric current either to said light or to said magnetic latch means, and rectifying means between said power supply means and said latch means for rectifying the current supplied to said latch means.

2. In a refrigerator, cabinet means forming an insulated food storage compartment having an access opening, a door for said access opening, gasket means between said door and said cabinet means, an evaporator arranged in thermal exchange relationship with the contents of said compartment, means including a motor-compressor unit for supplying liquefied refrigerant to said evaporator, magnetic latch means for holding said door in a closed position with said gasket in a compressed condition, a common power supply means for said motor-compressor unit, and said magnetic latch means, rectifying means for rectifying the current supplied to said magnetic latch means, said magnetic latch means including a coil for energizing the same, and means responsive to energization of said coil for interrupting the flow of current to said coil. 7

3. In a refrigerator, cabinet means forming an insulated food storage compartment having an access opening, a door for said access opening, gasket means between said door and said cabinet means, an evaporator arranged in thermal exchange relationship with the contents of said compartment, means including a motor-compressor unit for supplying liquefied refrigerant to said evaporator, magnetic latch means including an energizing coil for holding said door in a closed position with said gasket in a compressed condition, a common power supply means for said motor-compressor unit and said latch means, switch means operated in responseto closing of said door for controlling the supply of electric current to said latch means, rectifying means for rectifying the current supplied to said latch means, said magnetic latch means including a core portion and an armature forming with said core a closed magnetic fiux path when said door is in said closed position, means responsive to energization of said coil while said flux path is closed for interrupting the flow of current to said coil, and manual means for disengaging said armature from said core portion preparatory to opening said door.

4. In a latch for a refrigerator having a stationary frame member and a movable door member, gasket means condition, said latch means comprising an armature mounted on one of said members, a permanent magnet, and an electromagnet carried by the other of said members and cooperating with said armature and said permanent magnet to form a continuous metallic path for the magnetic flux to follow, means for momentarily energizing said electromagnet in response to closing of said door member, and means for reducing the permeance ratio of said path for said magnetic flux by introducing an air gap in said flux path.

5. In a safety magnetic latch for a refrigerator door or the like, an electromagnet having a core comprising one portion of magnetically hard metal and another portion of magnetically soft metal, an armature complementary to said core and forming with said core a continuous metallic flux path having a relatively high permeance ratio, means for momentarily energizing said electromagnet, and manual means for introducing an air gap in said flux path so as to reduce said permeance ratio for reducing the pull of said electromagnet.

6. In a refrigerator, a cabinet member, a door member, a gasket between said cabinet member and said door member, a magnetic latch for holding said door member in a fully closed position relative to said cabinet member with the pull-in position with the gasket only partially compressed, said magnetic latch comprising a keeper carried by one of said members, an electromagnet carried by the other of said members, said electromagnet having a core of magnetizable material, one portion of said core comprising magnetically soft material and another portion of said core comprising magnetically hard material, and means utilizing the residual magnetism of said core to hold said door member in said pull-in position preliminary to energization of said electromagnet for moving said door to said fully closed position.

7. In a refrigerator, a cabinet member, a door member, a gasket between said cabinet member and said door member, a magnetic latch for holding said door member in a closed position relative to said cabinet member, said magnetic latch comprising a keeper carried by one of said members, an electromagnet carried by the other of 75 her of magnetic material In said members, said electromagnet having a core of magnetizable material, one portion of said core comprising magnetically soft material and another portion of said core comprising magnetically hard material, said electromagnet including an energizing coil surrounding said magnetically hard portion of said core.

8. The combination, a casing member having an opening, a door member for closing said opening, a magnetic latch for holding said door member in the closed position, said magnetic latch comprising a magnetically soft keeper carried by one of said members and an electromagnet' carried by the other of said members, said electromagnet having a core comprising a portion of magnetically soft material and remainder of magnetically hard material, and a magnetically operable switch connected in series with said electromagnet magnetically opened by the strengthening of the magnetic fiield when the keeper is in contact with the electromagnet for deenergizing the electromagnet.

9. In an electromagnetic holding means, means forming a core member comprising a first portion of magnetically soft material and a second portion of magnetically hard material arranged in side-by-side relationship, a magnetizing coil surrounding a portion of said core member so as to establish magnetic poles of opposite polarity in hold said members in partially spaced relationship pending energization of said magnetizing coil.

10. In an electromagnetic holding means, means forming a core member, a magnetizing coil surrounding a portion of said core member so as to establish magnetic poles of opposite polarity in said core member, a keeper memvable into and out of engagement with said core member so as to form a magnetic flux path between said poles, energization of said magnetizing coil, said last named a portion arranged adjacent said to be actuated in response to a variation in the flux density of the flux in said flux path, and a manually operable keeper release member having means arranged with a larged mechanical advantage for manually releasing said keeper member from the magnetic hold of said core member.

11. In combination; a casing member having an opening; a door member for said opening; gasket means be tween said door member and said casing member; and a pressed or in a pull-in position without any appreciable pressure on said gasket means, said magnetic latch means including a core element of magnetic material supported on one of said members, a complementary keeper element supported on the other of said members, yieldable means of magnetic material carried by one of said elements for contacting the other of said elements in said pull-in position so as to utilize the residual magnetism of said elements to hold said door member in said pull-in position,

means and hold said door in said 12. A cabinet including walls surrounding a compartment provided with a door opening, a door pivoted to the walls for closing the door opening, a magnetic latch means for holding the door closed, said latch means comprising a member of magnetic material connected to said walls and a cooperating magnetic member and a pivotal connection pivotally connecting said cooperating member to the door, said door being provided with an external handle pivotally mounted on the door and having means providing a mechanical advantage for pivoting said cooperating member relative to the door to reduce the magnetic attraction between the membersof the latch means.

13. A cabinet ineluding Walls surrounding a compartment provided with a door opening, a door pivoted to the walls for closing the door opening, magnetic latch means for holding the door closed, said latchrneans comprising anelernent having a central portion in the form of an electromagnet having a core including a piece of permanent magnet material, said core having a branch portion of soft iron material extending from said central portion around the electromagnet, and a keeper extending substantially into contact With the core of said central portion and with said branch portion.

References Cited in the file of this patent UNITED STATES PATENTS Moyer July'l, 1930 Piesker v. 1, 1938 Perry Aug. 22, 1939 Smith Aug. 19, 1941 Morrison May 1, 1945 Mark et a1 May 31, 1949 Sherman Aug, 28, 1951 Manting Feb. 5, 1952 Fruh Ian. 6, 1953 Jacobs Mar. 16, 1954 Bachi June 26, 1956 

